Abstract: At present, the research on the coal pillar width of gob-side entry retaining focuses on the coal pillar strength, coal pillar load and coal pillar stability. There are few researches on the impact of rock heterogeneity and damage effects on the coal pillar width. Taking the gob-side entry retaining of No.12 coal in the fourth panel of Wulanmulun Coal Mine as the engineering background, the coal pillar width is studied in the context of rock heterogeneity-damage effect and the comprehensive use of theoretical analysis, numerical calculation and field measurement. The research results show that the rock heterogeneity-damage effect model can better reflect the fracture characteristics of the rock. Only a small number of particles are damaged in the elastic stage. Fractures begin to develop and penetrate in the plastic stage. Macro shear fractures along the diagonal direction are formed in the damage stage. As the coal pillar width increases, the overall deformation of the roadway first decreases and then increases. When the coal pillar width is 6 m, a sudden change occurs. The range and degree of damage around the coal pillar continue to decrease. The deformation of the roadway gang on the mining side is larger than that on the non-mining side. However, the amount of change with the coal pillar width is smaller than that of the non-mining side, and the surrounding rock damage distribution on the goaf side is larger than that of the solid coal side. According to the theoretical analysis and numerical calculation, it is proposed that the coal pillar width of gob-side entry retaining is 5 m. The result is applied to the engineering site. The overall deformation of the roadway in front of the working face is not large, and the movement and deformation of the overburden rock after 60 m behind the working face are basically stable, which verify the reasonableness of the coal pillar width of gob-side entry retaining.